Endovascular graft joint and method for manufacture

ABSTRACT

A joint and method for producing a joint in an endovascular graft. In one embodiment, a flap of a flexible material portion of an endovascular graft is folded about a portion of an expandable member to form a loop portion. The flap is secured in the loop configuration so that tensile force on the expandable member is transferred into a shear force on the fixed portion of the flap.

RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No. ______entitled “Method and Apparatus for Shape Forming Endovascular GraftMaterial”, by Chobotov, et al., U.S. patent application Ser. No. ______entitled “Method and Apparatus for Manufacturing an Endovascular GraftSection”, by Chobotov et al., and U.S. patent application Ser. No.______ entitled “Advanced Endovascular Graft”, by Chobotov et al. All ofthe above applications are commonly owned and were filed on even dateherewith. All of the above applications are hereby incorporated byreference, each in their entirety.

BACKGROUND

Embodiments of the device and method discussed herein relate to a systemand method for manufacturing intracorporeal devices used to replace,strengthen, or bypass body channels or lumens of patients; inparticular, those channels or lumens that have been affected byconditions such as abdominal aortic aneurysms.

Existing methods of treating abdominal aortic aneurysms include invasivesurgical methods with grafts used to replace the diseased portion of theartery. Although improvements in surgical and anesthetic techniques havereduced perioperative and postoperative morbidity and mortality,significant risks associated with surgical repair (including myocardialinfarction and other complications related to coronary artery disease)still remain.

Due to the inherent hazards and complexities of such surgicalprocedures, various attempts have been made to develop alternativerepair methods that involve the endovascular deployment of grafts withinaortic aneurysms. One such method is the non-invasive technique ofpercutaneous delivery of grafts and stent-grafts by a catheter-basedsystem. Such a method is described by Lawrence, Jr. et al. in“Percutaneous Endovascular Graft: Experimental Evaluation”, Radiology(1987). Lawrence et al. describe therein the use of a Gianturco stent asdisclosed in U.S. Pat. No. 4,580,568 to Gianturco. The stent is used toposition a Dacron® fabric graft within the vessel. The Dacron® graft iscompressed within the catheter and then deployed within the vessel to betreated.

A similar procedure is described by Mirich et al. in “PercutaneouslyPlaced Endovascular Grafts for Aortic Aneurysms: Feasibility Study,”Radiology (1989). Mirich et al. describe therein a self-expandingmetallic structure covered by a nylon fabric, the structure beinganchored by barbs at the proximal and distal ends.

An improvement to percutaneously delivered grafts and stent-graftsresults from the use of materials such as expandedpolytetrafluoroethylene (ePTFE) for a graft body. This material, andothers like it, have clinically beneficial properties. However,manufacturing a graft from ePTFE can be difficult and expensive. Forexample, it is difficult to bond ePTFE with conventional methods such asadhesives, etc. In addition, depending on the type of ePTFE, thematerial can exhibit anisotropic behavior. Grafts are generally deployedin arterial systems whose environments are dynamic and which subject thedevices to significant flexing and changing fluid pressure flow.Stresses are generated that are cyclic and potentially destructive tointerface points of grafts, particularly interface between soft andrelatively hard or high strength materials.

What has been needed is a method and device for manufacturingintracorporeal devices used to replace, strengthen or bypass bodychannels or lumens of a patient from ePTFE and similar materials whichis reliable, efficient and cost effective.

SUMMARY

An embodiment of the invention is directed to the formation of a jointbetween an connector member and a flexible material portion of anendovascular graft, or section thereof. A flap of the flexible materialportion is fixed about at least a portion of the connector member suchthat tensile force imposed on the connector member is transferred into ashear component of force on the fixed portion of the flap. Such aconfiguration provides a high strength joint with a low profile or lowcross sectional mass that will allow the graft to be compressed radiallyfor flexible low profile percutaneous delivery to a body conduit of apatient. Such a joining method also provides for ease of manufacture ofthe graft. The connector member can be an annular connector membersuitable for connection to an expandable.

Another embodiment of the invention is directed to an endovascular graftor section thereof with a flexible material portion and a transverselyor circumferentially oriented member secured to the flexible materialportion with a joint. The joint includes at least one flap of theflexible material folded back to form a loop portion about thetransversely or circumferentially oriented member. The flap is securedin the looped configuration. The flap for this embodiment and otherembodiments discussed herein can be secured in the loop configuration bya variety of methods including adhesive bonding and thermomechanicalcompaction or seam formation. Thermomechanical compaction which caninclude seam formation is particularly useful when fusible material isused for the flexible material portion. The transversely orcircumferentially oriented member may be a connector member, expandablestent, a portion of either of these or the like.

An embodiment of a method for securing a transversely orcircumferentially oriented member to a flexible material portion of anendovascular graft or section thereof is now described. A transverselyor circumferentially oriented member is disposed in proximity to a flapin the flexible material portion of the endovascular graft, or sectionthereof. The flap is then folded over at least a portion of thetransversely or circumferentially oriented member to form a loop portionof the flap about the transversely oriented member. The flap is thensecured in a looped configuration. The transversely or circumferentiallyoriented member may be an expandable stent, a connector memberconfigured to be secured to an expandable stent or other component of astent graft device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a layer of fusible material being positioned onto ashape forming mandrel.

FIG. 2 shows a first layer of fusible material disposed on a shapeforming mandrel.

FIG. 2A is a transverse cross sectional view of the first layer offusible material and the shape forming mandrel of FIG. 2 taken alonglines 2A-2A in FIG. 2.

FIG. 3 illustrates an additional layer of fusible material beingdeposited onto a shape forming mandrel.

FIG. 4 shows the first layer of fusible material being trimmed by aninstrument.

FIG. 5 is a transverse cross sectional view of the layers of fusiblematerial and shape forming mandrel of FIG. 5 taken along lines 5-5 ofFIG. 4.

FIG. 6 illustrates additional layers of fusible material being depositedon the shape forming mandrel.

FIG. 7 illustrates an inflation line being positioned on the first andadditional layers of fusible material of FIG. 6.

FIGS. 7A and 7B illustrate the formation of the inflation line of FIG.7.

FIG. 8 shows two expandable members positioned on the layers of fusiblematerial of FIG. 7.

FIG. 9 illustrates the deposition of an adhesive or melt processiblematerial adjacent a connector member of the graft body section underconstruction.

FIG. 10 shows another additional layer of fusible material beingdeposited onto the graft body section.

FIG. 11 illustrates excess fusible material being trimmed from the firstend and second end of the graft body section adjacent the connectormembers.

FIG. 12 is an elevational view of the graft body section with thefusible material trimmed away and removed.

FIG. 13A is a side view from the right hand side of a five axis seamforming apparatus.

FIG. 13B is a side view from the left hand side of a five axis seamforming apparatus.

FIG. 13C is a front view of the five axis seam forming apparatus ofFIGS. 13A and 13B.

FIG. 13D shows a stylus tip in contact with a transverse cross sectionedview of a cylindrical shape forming member with an axis of the stylustip oriented at an angle with the tangent of the shape forming member atthe point of contact therebetween.

FIG. 13E illustrates a stylus tip in contact with a plurality of layersof fusible material in a substantially flat configuration with thelongitudinal axis of the stylus tip at an angle with respect to a linewhich is orthogonal to the surface of the layers.

FIG. 13F is a front view of the seam forming apparatus with a shapeforming mandrel and a graft body section on the shape forming mandrelpositioned in the chuck of the seam forming member mount system.

FIG. 13G illustrates a distal extremity or tip of a stylus in contactwith the layers of fusible material of the graft body section.

FIG. 13H illustrates the tip of a stylus in contact with layers offusible material of the graft body section, forming a seam in thelayers.

FIG. 14 shows inflation channels being formed in the layers of fusiblematerial on the shape forming mandrel by the seam forming apparatusstylus tip.

FIG. 15 shows the graft body section with the channel formation completeand pressurized fluid being injected into an inflatable channel networkin order to expand the inflatable channels.

FIG. 16A illustrates one half of an embodiment of a two-piece mold foruse during expansion of the inflatable channels formed by the seamforming apparatus.

FIG. 16B is an end view showing the shape forming mandrel and graft bodysection within both halves of the mold.

FIG. 16C shows the graft body section and shape forming mandrel disposedwithin the mold cavity (with one half of the mold removed for clarity ofillustration) with a fluid being injected into the inflatable channelsof the graft body section in order to keep the inflatable channels in anexpanded state during the fixing or sintering of the fusible material.

FIG. 17 illustrates an outer layer or layers of fusible material beingforced into the mold cavity of a portion of the mold by pressurizedfluid as indicated by the dotted line.

FIG. 18 is an elevational view in partial section of an embodiment of aninflatable endovascular graft of the present invention.

FIG. 19 is an enlarged view of the graft of FIG. 18 taken at the dashedcircle indicated by numeral 19 in FIG. 18.

FIG. 20 is an enlarged view in section taken along lines 20-20 in FIG.18.

FIG. 21 is a transverse cross sectional view of the graft of FIG. 18taken along lines 21-21 in FIG. 18.

FIG. 22 is a transverse cross sectional view of the graft of FIG. 18taken along lines 22-22 in FIG. 18.

FIG. 23 is a transverse cross sectional view of the graft of FIG. 18taken along lines 23-23 in FIG. 18.

FIG. 24 is an elevational view in longitudinal section of an embodimentof an endovascular graft having features of the invention.

FIG. 25A is a transverse cross sectional view of a portion of theendovascular graft of FIG. 24 taken along lines 25A-25A of FIG. 24 whichillustrates an embodiment of a joint between a transversely orientedmember and flexible material portion of the endovascular graft.

FIG. 25B is a perspective view of the joint of FIG. 25A.

FIG. 26 is a transverse cross sectional view of a portion of anendovascular graft which illustrates an embodiment of a joint between atransversely oriented member and flexible material portion of theendovascular graft.

FIG. 27 is a transverse cross sectional view of a portion of anendovascular graft which illustrates an embodiment of a joint between atransversely oriented member and flexible material portion of theendovascular graft.

FIG. 28 is a perspective view of a method for manufacturing anendovascular graft wherein a flap of a flexible material portion of theendovascular graft is being formed in a loop about a transverselyoriented member.

FIG. 29 is a perspective view of the endovascular graft of FIG. 28 witha plurality of flaps of the flexible material portion of theendovascular graft being formed in loops about portions of thetransversely oriented member.

FIG. 30 illustrates a perspective view of the endovascular graft ofFIGS. 28 and 29 with an outer layer of flexible material disposed overthe flap portions.

FIG. 31 illustrates a tubular section of an endovascular graft having afirst layer of flexible material and a second layer of flexible materialwherein flaps of flexible material have been formed in the second layerof flexible material, formed in loop portions about transverselyoriented members and secured in a looped configuration about thetransversely oriented members.

DETAILED DESCRIPTION

FIG. 1 illustrates a sheet of fusible material 10 stored on an elongatedrum 11. The drum 11 is rotatable, substantially circular in transversecross section and has a transverse dimension in the longitudinal center12 that is greater than the transverse dimension of either end of thedrum. The sheet of fusible material 10 is being rolled from the elongatedrum in a single layer 13 onto an interior surface support means in theform of a cylindrical or tapered (conical) shape forming member ormandrel 14 to form a body section 15 of an endovascular graft 16. Thebody section 15 has a proximal end 17 and a distal end 18. For thepurposes of this application, with reference to endovascular graftdevices, the proximal end 17 describes the end of the graft that will beoriented towards the oncoming flow of bodily fluid, usually blood, whenthe device is deployed within a conduit of a patient's body. The distalend 18 of the graft is the end opposite the proximal end.

A single layer of fusible material 13 is a term that generally refers toa sheet of material that is not easily separated by mechanicalmanipulation into additional layers. The shape forming mandrel 14 issubstantially cylindrical in configuration, although otherconfigurations are possible. Middle section 20 of mandrel 14 shown inFIGS. 1-2 has a transverse dimension which is smaller than thetransverse dimension of a first end section 21 and a second end section22. The shape forming mandrel may have a first tapered section 23 at thefirst end and a second tapered section 24 at the second end. The sheetof fusible material 10 is shown being rolled off the elongate drum 11 inthe direction indicated by the arrow 11A with the lead end 25 of thefirst layer of fusible material 10 oriented longitudinally along anoutside surface 14A of the shape forming mandrel 14.

The fusible material in the embodiment illustrated in FIG. 1 is ePTFEthat ranges from about 0.0005 to about 0.010 inch in thickness;specifically from about 0.001 to about 0.003 inch in thickness. Thesheet being disposed or rolled onto the shape forming mandrel 14 mayrange from about 2 to about 10 inches in width; specifically, from about3 to about 7 inches in width, depending on the indication and size ofthe end product.

The ePTFE material sheet 10 in FIG. 1 is a fluoropolymer with a node andfibril composition with the fibrils oriented in primarily a uniaxialdirection substantially aligned with the longitudinal axis of shapeforming mandrel 14. Other nodal/fibril orientations of ePTFE could alsobe used for this layer, including multiaxially oriented fibrilconfigurations or uniaxial material oriented substantiallycircumferentially about shape forming mandrel 14 or at any desired anglebetween substantial alignment with the longitudinal axis and substantialalignment with a circumferential line about the shape forming mandrel14. Uniaxially oriented ePTFE materials tend to have greater tensilestrength along the direction of fibril orientation, so fibrilorientation can be chosen to accommodate the greatest stresses imposedupon the finished product for the particular layer, combination oflayers, and portion of the product where such stress accommodation isneeded.

The layers of fusible material made of ePTFE are generally applied orwrapped in an unsintered state. By applying the ePTFE layers in anunsintered or partially sintered state, the graft body section 15, uponcompletion, can then be sintered or fixed as a whole in order to form acohesive monolithic structure with all contacting surfaces of ePTFElayers achieving some level of interlayer adhesion. It may, however, bedesirable to apply some layers of fusible material that have beenpre-sintered or pre-fixed in order to achieve a desired result or toassist in the handling of the materials during the construction process.For example, it may be desirable in some embodiments to sinter thesingle layer 13 of fusible material applied to the shape forming mandrel14 in order to act as a better insulator between the shape formingmandrel 14, which can act as a significant heat sink, and subsequentlayers of fusible material which may be welded by seam formation in somelocations in order to create inflatable channels.

The amount of expansion of the ePTFE material used for the constructionof endovascular grafts and other devices can vary significantlydepending on the desired characteristics of the material and thefinished product. Typically, the ePTFE materials processed by thedevices and methods discussed herein may have a density ranging fromabout 0.4 to about 2 grams/cc; specifically, from about 0.5 to about 0.9grams/cc. The nodal spacing of the uniaxial ePTFE material may rangefrom about 0.5 to about 200 microns; specifically, from about 5 to about35 microns. The nodal spacing for multiaxial ePTFE material may rangefrom about 0.5 to about 20 microns; specifically, from about 1 to about2 microns.

Although FIG. 1 illustrates a layer of fusible material that is made ofePTFE, the methods described herein are also suitable for a variety ofother fusible materials. Examples of other suitable fusible materialsfor endovascular graft construction and other applications include PTFE,porous PTFE, ultra high molecular weight polyethylene, polyesters, andthe like.

FIGS. 2 and 2A depict a first layer of fusible material 26 disposed onthe shape forming mandrel 14 with an overlapped portion 27 of the firstlayer 26 on itself. A terminal end 28 of the first layer 26 is seenextending longitudinally along the length of the shape forming mandrel14. As the layer of fusible material is wrapped onto shape formingmandrel 14, some tension may be provided on the sheet of material by theelongate drum 11. As a result of this tension and the flexible andconforming properties of the ePTFE material, the first layer of material26 conforms closely to the outer contour of the shape forming mandrel 14as is illustrated in FIG. 2.

In some embodiments, it may be desirable to pass the tip of a seamforming tool or similar device (not shown) along the overlapped portion27 of first layer 26 in a longitudinal direction in order to form a seam(not shown) along the overlapped portion 27 of first layer 26. A toolsuitable for forming such a longitudinal seam is a soldering iron with asmooth, rounded tip that will not catch or tear the layer of fusiblematerial. An appropriate operating temperature for the tip of such atool may range from about 320 to about 550 degrees Celsius;specifically, from about 380 to about 420 degrees Celsius.

FIG. 3 illustrates an additional layer of fusible material 30 beingdisposed or wrapped onto the first layer of fusible material 26 in amanner similar to that described above for the first layer 26. Bothuniaxial and multiaxial ePTFE may be used for this additional layer 30.A lead end 31 of the additional layer can be seen adjacent the terminalend 28 of the first layer 26. Tension on the additional layer of fusiblematerial 30 helps to make the additional layer 30 conform to the shapeforming mandrel 14 as seen in the illustration. Although a singleadditional layer 30 is shown in FIG. 3 as being disposed onto the firstlayer 26, it is within the scope of the invention to wrap multipleadditional layers 30 of fusible material in this step. We have foundthat wrapping two additional layers 30 of multiaxial ePTFE onto thefirst layer 26 helps to form a useful graft body section 15.

FIG. 4 shows an optional step in which the first and additional layersof fusible material 26 and 30 which form the graft body section 15 underconstruction are trimmed by knife edge 32 or a similar tool which ispressed against the layers of material and moved circumferentially aboutthe shape forming mandrel 14. FIG. 5 is a transverse cross sectionalview of the shape forming mandrel 14 and graft body section 15 of FIG. 5taken along lines 5-5 in FIG. 4. The overlapped portion 27 of the firstlayer 26 and an overlapped portion 33 of the additional layer 30 offusible material can be seen. It may be desirable to create alongitudinal seam in the overlapped portion 33 of the additional layer30 in a manner similar to that of the first layer 26 discussed aboveusing the same or similar tools.

FIG. 6 illustrates a proximal end wrap 34 of fusible material beingapplied to the additional layer 30 of graft body section 15, preferablyunder some tension. We have found it useful to have end wrap 34 beuniaxial ePTFE, with the fibrils of the end wrap material orientedcircumferentially about the shape forming mandrel 14, although otherorientations and types of ePTFE are possible. The end wrap material mayhave a thickness ranging from about 0.0005 to about 0.005 inch;specifically, from about 0.001 to about 0.002 inch. The width of the endwrap material may range from about 0.25 to about 2.0 inch; specifically,from about 0.5 to about 1.0 inch. One or more layers of end wrap 34 (inany desired orientation) may be built up onto the proximal end 17 ofgraft body section 15 on shape forming mandrel 14. The additional endwrap layer or layers 34 may be applied in a manner similar to that ofthe first layer 26 and additional layers 30 as discussed above.

FIG. 7 shows graft body section 15 with the end wrap layer 34 completedwith an inflation line 36 disposed on or near the distal end 18 of graftbody section 15. The inflation line 36 may be constructed as shown inFIGS. 7A and 7B of ePTFE by wrapping one or more layers of the materialabout a cylindrical mandrel 37. A longitudinal seam 38 can then beformed in an overlapped portion of the layers by passing the tip of aseam forming tool 39 along the overlapped portion of the first layer ina longitudinal direction in order to form a seam 38 along the overlappedportion of the layers of the inflation line 36. A tool suitable forforming such a longitudinal seam is a soldering iron with a smoothrounded tip that will not catch or tear the layer of fusible material;operating temperatures for the tip may range as previously discussed.Alternatively, the inflation line 36 may be formed using an ePTFEextrusion placed over a mandrel.

Once seam 38 is formed in inflation line 36, the fusible material ofinflation line 36 may can be fixed or sintered by heating to apredetermined temperature for a predetermined time. For embodiments ofthe inflation line 36 made of ePTFE, the layers are sintered by bringingthe layered assembly to a temperature ranging from about 335 to about380 degrees Celsius (for unsintered material) and about 320 to about 380degrees Celsius (for sintering material that was previously sintered)and then cooling the assembly to a temperature ranging from about 180 toabout 220 degrees Celsius. The inflation line 36 may then be removedfrom mandrel 37 and disposed on a graft body assembly 40 as shown inFIG. 7. The inflation line 36 may be pre-fixed or pre-sintered to avoidhaving the inner surfaces of the inflation line 36 stick together duringthe construction and processing of the graft and possibly block theinflation line 36.

In FIG. 8, expandable members in the form of a proximal connector member41 and a distal connector member 42 have been disposed onto the graftbody section 15 towards the respective graft body section proximal end17 and distal end 18. The proximal connector member 41 is an elongateflexible metal element configured as a ring, with the ring having azig-zag or serpentine pattern around the circumference of the ring. Thedistal connector member 42 can have a similar configuration; note thefeature of this element in which an extended apex 44 is disposed overinflation line 36 to further stabilize graft section 15. Thisconfiguration allows the connector members 41 and 42 to be radiallyconstrained and radially expanded while maintaining a circular ringconfiguration. The embodiment of the connector members 41 and 42 shownin FIG. 8 may be constructed of any suitable biocompatible material;most suitable are metals, alloys, polymers and their composites known tohave superelastic properties that allow for high levels of strainwithout plastic deformation, such as nickel titanium (NiTi). Otheralloys such as stainless steel may also be used. Connector members 41and 42 shown are also configured to be self-expanding from a radiallyconstrained state. The serpentine pattern of the connector members 41and 42 is disposed over base layers of the graft body section as areconnector elements 43 which are disposed on certain apices 44 of theserpentine pattern of the connector members 41 and 42. The embodimentsof the connector members 41 and 42 shown in FIG. 8 have been shapeformed to lie substantially flat against the contour of the outersurface of the shape forming mandrel 14. Although the embodiment of FIG.8 illustrates connector members 41 and 42 being disposed upon the graftbody section 15, expandable members including stents or the like may beused in place of the connector members 41 and 42.

An optional adhesive or melt-processible material such as FEP or PFA maybe deposited adjacent the connector members 41 and 42 prior to theaddition of additional layers of fusible material to the graft bodysection 15, as is shown in FIG. 9. Materials such as FEP or PFA can helpthe layers of fusible material to adhere to the connector members 41 and42, to inflation line 36 (in the case of distal member 42), and to eachother. In addition, such material may serve to provide strain reliefbetween connector members 41 and 42 and the adhered or bonded layers offusible material (and inflation line 36) adjacent the wire of theconnector members 41 and 42. It has been determined that one of theareas of greatest concentrated stress within an endovascular structuresuch as that described herein, when deployed within a dynamic biologicalsystem, such as an artery of a human patient, is at the junction betweenthe connector members 41 and 42 and graft body section 15. Therefore, itmay be desirable to include materials such as FEP or PFA or some otherform of strength enhancement or strain relief in the vicinity of thisjunction.

An outer overall wrap layer 50 may thereafter be applied to the graftbody section 15 and connector members 41 and 42 as shown in FIG. 10. Theouter overall wrap layer 50 can include one, two, three or more layersof multiaxial ePTFE, usually about 2 to about 4 layers, but uniaxialePTFE other suitable fusible materials, fibril orientation and layernumbers could also be used. The outer overall wrap layer 50 is mostusefully applied under some tension in order for the layer or layers tobest conform to the outer contour of the shape forming mandrel 14 andgraft body section 15. When the outer layer 50 comprises multiaxialePTFE, there is generally no substantially preferred orientation ofnodes and fibrils within the microstructure of the material. This resultin a generally isotropic material whose mechanical properties, such astensile strength, are generally comparable in all directions (as opposedto significantly different properties in different directions foruniaxially expanded ePTFE). The density and thickness of the multiaxialmaterial can be the same as or similar to those dimensions discussedabove.

Although not shown in the figures, we have found it useful to add one ormore-optional cuff-reinforcing layers prior to the addition of anoverall wrap layer 50 as discussed below in conjunction with FIG. 10.Typically this cuff-reinforcing layer is circumferentially applied tograft body section 15 at or near the graft body section proximal end 17so to provide additional strength to the graft body section proximal end17 in those designs in which a proximal cuff (and possibly a proximalrib) are used. Typically the graft experiences larger strains duringfabrication and in service in the region of the proximal cuff,especially if a larger cuff is present. This optional cuff-reinforcinglayer typically is multiaxial ePTFE, although uniaxial ePTFE and othermaterials may be used as well. We have found effective acuff-reinforcing layer width from about 20 to about 100 mm;specifically, about 70 mm. Functionally, however, any width sufficientto reinforce the proximal end of graft body section 15 may be used.

Once the additional layer or layers of fusible material and additionalgraft elements such as the connector members 41 and 42 and inflationline 36 have been applied, any excess fusible material may be trimmedaway from the proximal end 17 and distal end 18 of graft body section15. FIG. 11 illustrates one or more layers of fusible material beingtrimmed from the proximal end 17 and distal end 18 of the graft bodysection 15 so as to leave the connector members 41 and 42 embeddedbetween layers of fusible material but with the connector elements 43exposed and a distal end 51 of the inflation line 36 exposed as shown inFIG. 12. Once the fusible material has been trimmed from the proximalend 17 and the distal end 18, as discussed above, an additional processmay optionally be performed on the proximal end 17, distal end 18 orboth the proximal end and distal end 17 and 18. In this optional process(not shown in the figures), the outer wrap 50 is removed from a portionof the connector members 41 and 42 so as to expose a portion of theconnector members 41 and 42 and the additional layer of fusible material30 beneath the connector member 42 and the proximal end wrap 34 beneathconnector member 41. Once exposed, one or more layers of the additionallayer or layers 30 or proximal end wrap 34 may have cuts made therein toform flaps which can be folded back over the respective connectormembers 42 and 41 and secured to form a joint (not shown). One or morelayers of fusible material can then be disposed over such a joint toprovide additional strength and cover up the joint. The construction ofsuch a joint is discussed in copending U.S. Patent Application“Endovascular Graft Joint and Method for Manufacture” by Chobotov et al.which has been incorporated by reference herein.

Once the graft body section 15 has been trimmed, the entire shapeforming mandrel 14 and graft body section 15 assembly is moved to a seamforming apparatus 52 illustrated in FIGS. 13A-13H. This seam formingapparatus 52 has a base 53 and a vertical support platform 54 whichextends vertically upward from the back edge of the base 53. A mountsystem 55 is secured to the base 53 and for the embodiment shown in thefigures, consists of a motor drive chuck unit 56 secured to a riser 57and a live center unit 58 secured to a riser 59. Both risers 57 and 59are secured to the base 53 as shown. The axis of rotation 55A of thechuck 60 of the motor drive chuck unit 56 and the axis of rotation 55Bof the live center 61 of the live center unit 58 are aligned orconcentric as indicated by dashed line 55C. A motor is mechanicallycoupled to the chuck 60 of the motor drive chuck unit 56 and serves torotate the chuck 60 in a controllable manner.

A vertical translation rack 62 is secured to the vertical supportplatform 54 and extends from the base 53 to the top of the verticalsupport platform 54. A vertical car 63 is slidingly engaged on thevertical translation rack 62 and can be moved along the verticaltranslation rack 62, as shown by arrows 63A, in a controllable manner bya motor and pinion assembly (not shown)-secured to the vertical car 63.A horizontal translation rack 64 is secured to the vertical car 63 andextends from the left side of the vertical car 63 to the right side ofthe vertical car 63. A horizontal car 65 is slidingly engaged on thehorizontal translation rack 64 and can be moved along the horizontalrack 64, as shown by arrow 64A, in a controllable manner by a motor andpinion assembly (not shown) which is secured to the horizontal car 65.

A stylus rotation unit 66 is slidingly engaged with a second horizontaltranslation rack 65A disposed on the horizontal car 65 and can be movedtowards and away from the vertical car 63 and vertical support platform54 in a controllable manner as shown by arrow 66A. A stylus rotationshaft 67 extends vertically downward from the stylus rotation unit 66and rotates about an axis as indicated by dashed line 67B and arrow 67Ain a controllable manner. A stylus mount 68 is secured to the bottom endof the rotation shaft 67 and has a main body portion 69 and a styluspivot shaft 70. A stylus housing 71 is rotatably secured to the stylusmount 68 by the stylus pivot shaft 70. A torsion spring 72 is disposedbetween the proximal end of the stylus housing 73 and the stylus mount68 and applies a predetermined amount of compressive, or spring-loadedforce to the proximal end 73 of the stylus housing 71. This in turndetermines the amount of tip pressure applied by a distal extremity 80of a stylus tip 75 disposed at the distal end section 78 of the stylus79 (which is in turn secured to the distal end section 76 of the stylushousing 71).

The base 53 of seam forming apparatus 52 is secured to a control unithousing 77 which contains one or more power supplies, a CPU, and amemory storage unit that are used in an automated fashion to controlmovement between the graft body 15 section and the stylus tip 75 in thevarious degrees of freedom therebetween. The embodiment of the seamforming apparatus 52 described above has five axes of movement (ordegrees of freedom) between an object secured to the chuck 60 and livecenter 61 and the stylus tip 75; however, it is possible to haveadditional axes of movement, such as six, seven, or more. Also, for someconfigurations and seam forming processes, it may be possible to usefewer axes of movement, such as two, three, or four. In addition, anynumber of configurations may be used to achieve the desired number ofdegrees of freedom between the stylus 79 and the mounted device. Forexample, additional axes of translation or rotation could be added tothe mount system and taken away from the stylus rotation unit 66.Although the embodiment of the shape forming mandrel 14 shown in FIGS.1-17 is cylindrical, a five axis or six axis seam forming apparatus hasthe capability and versatility to accurately create seams of most anydesired configuration on a shape forming member or mandrel of a widevariety of shapes and sizes. For example, a “Y” shaped mandrel suitablefor generating a bifurcated graft body section could be navigated by thefive axis seam forming apparatus illustrated herein, as well as othershapes. Finally, seam forming apparatus 52 illustrated herein is but oneof a number of devices and configurations capable of achieving the seamsof the present inventions.

FIG. 13D illustrates an enlarged view of a stylus tip 75 applied to arotating cylindrical surface 86B with the surface rotating in acounterclockwise direction as indicated by arrow 86A. The cylindricalsurface can support one or more layers of fusible material (not shown)between the distal extremity 80 of the stylus tip 75 and the surface 86Bwhich require seam to be formed therein. The stylus tip 75 has alongitudinal axis that forms an angle 86 with a tangent to the surfaceof the cylindrical surface indicated by dashed line 87. Although notnecessary, we have found it useful to have the object in contact withthe stylus tip 75 rotating or moving in a direction as show in FIG. 13D,relative to angle 86 in order to prevent chatter of the configuration ordistortion of fusible material on the surface 86A. In one embodiment,angle 86 may range from about 5 to about 60 degrees; specifically, fromabout 10 to about 20 degrees. It is also useful if the distal extremity80 of the stylus tip 75 has a smooth surface and is radiused. A suitableradius for one embodiment may range from about 0.01 to about 0.030 inch;specifically, from about 0.015 to about 0.02 inch.

FIG. 13E shows a similar relationship between a stylus tip 75 and hardsurface 81. Surface 81 may have one or more layers of fusible material(not shown) disposed thereon between distal extremity 80 and surface 81.A longitudinal axis 75A of stylus tip 75 forms an angle 86 with thedashed line 89 that is parallel to surface 81. Angle 88 in thisembodiment should range from about 5 to about 60 degrees; specifically,from about 10 to about 20 degrees, so to ensure smooth relative motionbetween surface 81 and tip 75. The surface 81 is shown moving relativeto the stylus tip 75 in the direction indicated by arrow 81A.

The pressure exerted by the extremity 80 of stylus tip 75 on thematerial being processed is another parameter that can affect thequality of a seam formed in layers of fusible material. In oneembodiment in which the stylus tip is heated, the pressure exerted bythe distal extremity 80 of the stylus tip 75 may range from about 100 toabout 6,000 pounds per square inch (psi); specifically, from about 300to about 3,000 psi. The speed of the heated stylus 75 relative to thematerial being processed, such as that of graft body section 15, mayrange from about 0.2 to about 10 mm per second, specifically, from about0.5 to about 1.5 mm per second. The temperature of the distal extremity80 of the heated stylus tip 75 in this embodiment may range from about320 to about 550 degrees Celsius; specifically, about 380 to about 420degrees Celsius.

Seam formation for ePTFE normally occurs by virtue of the application ofboth heat and pressure. The temperatures at the tip of the heated stylus75 during such seam formation are generally above the melting point ofhighly crystalline ePTFE, which may range be from about 327 to about 340degrees Celsius, depending in part on whether the material is virginmaterial or has previously been sintered). In one embodiment, the stylustip temperature for ePTFE welding and seam formation is about 400degrees Celsius. Pressing such a heated tip 75 into the layers of ePTFEagainst a hard surface such as the outside surface of the shape formingmandrel) compacts and heats the adjacent layers to form a seam withadhesion between at least two of, if not all, the layers. At the seamlocation and perhaps some distance away from the seam, the ePTFEgenerally transforms from an expanded state with a low specific gravityto a non-expanded state (i.e., PTFE) with a relatively high specificgravity. Some meshing and entanglement of nodes and fibrils of adjacentlayers of ePTFE may occur and add to the strength of the seam formed bythermal-compaction. The overall result of a well-formed seam between twoor more layers of ePTFE is adhesion that can be nearly as strong or asstrong as the material adjacent the seam. The microstructure of thelayers may change in the seam vicinity such that the seam will beimpervious to fluid penetration.

It is important to note that a large number of parameters determine theproper conditions for creating the fusible material seam, especiallywhen that material is ePTFE. Such parameters include, but are notlimited to, the time the stylus tip 75 is in contact with the material(or for continuous seams, the rate of tip movement), the temperature (ofthe tip extremity 80 as well as that of the material, the underlyingsurface 81, and the room), tip contact pressure, the heat capacity ofthe material, the mandrel, and the other equipment, the characteristicsof the material (e.g. the node and fibril spacing, etc.), the number ofmaterial layers present, the contact angle between the tip extremity 80and the material, the shape of the extremity 80, etc. Knowledge of thesevarious parameters is useful in determining the optimal combination ofcontrollable parameters in forming the optimal seam. And althoughtypically a combination of heat and pressure is useful in forming anePTFE seam, under proper conditions a useful seam may be formed bypressure at ambient temperature (followed by elevation to sinteringtemperature); likewise, a useful seam may also be formed by elevatedtemperature and little-to-no applied pressure.

For example, we have created seams in ePTFE that formed an intact,inflatable cuff by the use of a clamshell mold that presented aninterference fit on either side of a cuff zone for the ePTFE. Theapplication of pressure alone without using an elevated temperatureprior to sintering formed a seam sufficient to create a working cuff.

FIG. 13F depicts a front view of the seam forming apparatus 52 with ashape forming mandrel 14 secured to the chuck 60 and the live centerunit 58. The distal extremity of the heated stylus tip 75 is in contactwith the graft body section 15 which is disposed on the shape formingmandrel 14. The chuck 60 is turning the shape forming mandrel 14 andgraft body section 15 in the direction indicated by the arrow 60A toform a seam 81 between the layers of fusible material of the graft bodysection 15.

FIGS. 13G and 13H illustrate an enlarged view of the heated stylus tip75 in contact with the graft body section 15 in the process of creatingone ore more seams 81 which are configured to form elongate inflatablechannels 82 in the graft body section 15. The term “inflatable channels”may generally be described herein as a substantially enclosed orenclosed volume between layers of fusible material on a graft or graftsection, and in some embodiments, in fluid communication with at leastone inlet port for injection of inflation material. The enclosed volumeof an inflatable channel or cuff may be zero if the inflatable cuff orchannel is collapsed in a non-expanded state. The enclosed volume of aninflatable channel may or may not be collapsible during compression orcompacting of the graft body section 15.

FIG. 13H is an enlarged view in section of the distal extremity 80 ofthe heated stylus tip 75 in contact with layers of fusible material ofgraft body section 15. The layers of fusible material are being heatedand compressed to form a bond 15A therebetween. The seam formingapparatus can position the distal extremity 80 at any desired locationon the graft body section 15 by activation of one or more of the fivemotors controlled by the components in the control unit housing 77. Eachof the five motors controls relative movement between graft body section15 and distal extremity 80 in one degree of freedom. Thus, the distalextremity 80 may be positioned above the surface of the graft bodysection 15, as shown in FIG. 13C, and brought to an appropriatetemperature for seam formation, as discussed above, by resistive heatingor any other appropriate method. Once extremity 80 has reached thetarget temperature, it can be lowered by activation of the motor whichcontrols movement of the vertical car. The extremity 80 can be loweredand horizontally positioned by other control motors until it contactsthe graft body section in a desired predetermined position on graft bodysection 15, as shown in FIG. 13F.

Once distal extremity 80 makes contact with graft body section 15 withthe proper amount of pressure, it begins to form a seam between thelayers of the fusible material of the graft body section as shown inFIG. 13H. The pressure or force exerted by the extremity 80 on the graftbody section may be determined by the spring constant and amount ofdeflection of torsion spring 72 shown in FIGS. 13A and 13B; generally,we have found a force at the extremity 80 ranging from about 0.2 toabout 100 grams to be useful. As the seam formation process continues,the surface of graft body section 15 may be translated with respect tothe distal extremity 80 while desirably maintaining a fixed,predetermined amount of pressure between the distal extremity 80 and thelayers of fusible material of the graft body section. The CPU (or anequivalent device capable of controlling the components of apparatus 52)of the control unit housing 77 may be programmed, for instance, amathematical representation of the outer surface contour of any knownshape forming member or mandrel.

The CPU is thereby able to control movement of the five motors ofapparatus 52, so that distal extremity 80 may follow the contour of theshape forming member while desirably exerting a fixed predeterminedamount of pressure the layers of fusible material disposed between thedistal extremity 80 and the shape forming member. While seam formationis taking place, the pressure exerted by the distal extremity 80 on theshape forming member may be adjusted dynamically. The extremity 80 mayalso be lifted off the graft body section and shape forming member inlocations where there is a break in the desired seam pattern. Oncedistal extremity 80 is positioned above the location of the startingpoint of the next seam following the break, the extremity 80 may then belowered to contact the layers of fusible material, reinitiating the seamformation process.

Use of the seam forming apparatus 52 as described herein is but one of anumber of ways to create the desired seams in the graft body section 15of the present invention. Any suitable process and apparatus may be usedas necessary and the invention is not so limited. For instance, seamsmay also be formed in a graft body section 15 by the use of a fully orpartially heated clamshell mold whose inner surfaces contain raisedseam-forming extensions. These extensions may be configured andpreferentially or generally heated so that when the mold halves areclosed over a graft body section 15 disposed on a mandrel, theextensions apply heat and pressure to the graft body section directlyunder the extensions, thereby “branding” a seam in the graft bodysection in any pattern desired and in a single step, saving much timeover the technique described above in conjunction with seam formingapparatus 52.

If the fusible material comprises ePTFE, it is also possible to infuseor wick an adhesive (such as FEP or PFA) or other material into theePTFE layers such that the material flows into the fibril/node structureof the ePTFE and occupies the pores thereof. Curing or drying thisadhesive material will mechanically lock the ePTFE layers togetherthrough a continuous or semi-continuous network of adhesive material nowpresent in and between the ePTFE layers, effectively bonding the layerstogether.

FIG. 14 illustrates a substantially completed set of seams 81 formed inthe layers of fusible material of the graft body section 15, which seamsform inflatable channels 82. FIG. 15 illustrates graft body section 15as fluid (such as compressed gas) is injected into the inflation line 36and in turn into the inflatable channel network 84 of body section 15,as shown by arrow 84A. The fluid is injected to pre-stress theinflatable channels 82 of body section 15 and expand them outwardradially. The fluid may be delivered or injected through an optionalelongate gas containment means having means for producing a permeabilitygradient in the form of a manifold or pressure line 85. The pressureline 85 shown in FIG. 15 has a configuration with an input (not shown)located outside the inflation line and a plurality of outlet aperturesor orifices (not shown) that may be configured to provide an evendistribution of pressure within the inflatable channel network 84. Otherfluid injection schemes and configurations are of course possible.

Because ePTFE is a porous or semi-permeable material, the pressure ofexerted by injected fluids such as pressurized gas tends to drop off ordiminish with increasing distance away from the outlet apertures ororifices (not shown) of manifold or pressure line 85. Therefore, in someembodiments, pressure line 85 may comprise apertures or orifices (notshown) which, when disposed in graft body section 15, progressivelyincreases in size as one moves distally along the pressure line towardsthe proximal end 17 graft body section 15 in order to compensate for adrop in pressure both within the inflatable channel network 84 andwithin the manifold or pressure line 85 itself.

Once some or all of the inflatable channels 82 have been pre-expanded orpre-stressed, the graft body section 15 and shape forming mandrelassembly 89 may then be positioned within an outer constraint means inthe form of a mold to facilitate the inflatable channel expansion andsintering process. One half of a mold 90 suitable for forming anembodiment of a graft body section 15 such as that shown in FIG. 15 isillustrated in FIG. 16A. A mold half body portion 91 is one of twopieces of mold 90. A mold similar to mold 90 could be made from anynumber of mold body portions configured to fit together. For example, amold 90 could be designed from three, four, five or more mold bodyportions configured to fit together to form a suitable main cavityportion 93 for maintaining the shape of graft body section 15 duringchannel expansion and sintering. For certain configurations, a one-piecemold may be used.

Mold body portion 91 has a contact surface 92 and a main cavity portion93. Main cavity portion 93 has an inside surface contour configured tomatch an outside surface contour of the graft body section with theinflatable channels in an expanded state. Optional exhaust channels 92Amay be formed in contact surface 92 and provide an escape flow path forpressurized gas injected into the inflatable channel network 84 duringexpansion of the inflatable channels 82.

The main cavity portion 93 of the FIGS. 16A-16B embodiment issubstantially in the shape of a half cylinder with circumferentialchannel cavities 94 for forming the various inflatable channels 82 ofgraft body section 15. Cavity 93 has a first tapered portion 95 at theproximal end 96 of mold 90 and a second tapered portion 97 at the molddistal end 98. FIG. 16B shows an end view of mold 90 with the two moldbody portions 91 and 100 pressed together with the assembly of the graftbody section 15 and shape forming mandrel 14 disposed mold cavity 93.

FIG. 16C shows the assembly of the graft body section 15 and shapeforming mandrel 14 disposed within mold 90, with the circumferentialinflatable channels 82 of the graft body section 15 aligned with thecircumferential channel cavities 94 of the main cavity portion 93. Onemold body portion 100 of mold 90 is not shown for the purpose of clarityof illustration. A pressurized fluid indicated as being delivered orinjected into manifold or pressure line 85 by arrow 85A.

FIG. 17 illustrates by the phantom lines how the outer layers 94A ofcircumferential inflatable channel 82 of the fusible material of a graftbody section 15 are expanded into the circumferential channel cavity 94of mold cavity 93. The direction of the expansion of the outer layers94A to the position indicated by the phantom lines is indicated by arrow94B. A cross sectional view of the seams 83 of the circumferentialinflatable channel 82 is shown in FIG. 17 as well.

While the graft body section network of inflatable channels 84 is in anexpanded state by virtue of pressurized material being delivered orinjected into pressure line 85, the entire assembly may be positionedwithin an oven or other heating device (not shown) in order to bring thefusible material of graft body section 15 to a suitable temperature foran appropriate amount of time in order to fix or sinter the fusiblematerial. In one embodiment, the fusible material is ePTFE and thesintering process is carried out by bringing the fusible material to atemperature of between about 335 and about 380 degrees Celsius;specifically, between about 350 and about 370 degrees Celsius. The moldmay then be cooled and optionally quenched until the temperature of themold drops to about 250 degrees Celsius. The mold may optionally furtherbe quenched (for handling reasons) with ambient temperature fluid suchas water. Thereafter, the two halves 91 and 100 of mold 90 can be pulledapart, and the graft assembly removed.

The use of mold 90 to facilitate the inflatable channel expansion andsintering process is unique in that the mold cavity portion 93 acts as abackstop to the graft body section so that during sintering, thepressure created by the injected fluid that tends to expand theinflatable channels outward is countered by the restricting pressureexerted by the physical barrier of the surfaces defining the mold cavity93. In general terms, therefore, it is the pressure differential acrossthe inflatable channel ePTFE layers that in part defines the degree ofexpansion of the channels during sintering. During the sintering step,the external pressure exerted by the mold cavity surface competes withthe fluid pressure internal to the inflatable channels (kept at a levelto counteract any leakage of fluid through the ePTFE pores at sinteringtemperatures) to provide an optimal pressure differential across theePTFE membrane(s) to limit and define the shape and size of theinflatable channels.

Based on this concept, we have found it possible to use alternatives toa mold in facilitating the inflatable channel expansion process. Forinstance, it is possible inject the channel network with a working fluidthat does not leak through the ePTFE pores and to then expand thenetwork during sintering in a controlled manner, without any externalconstraint. An ideal fluid would be one that could be used within thedesired ePTFE sintering temperature range to create the necessarypressure differential across the inflatable channel membrane and theambient air, vacuum, or partial vacuum environment so to control thedegree of expansion of the channels. Ideal fluids are those that possessa high boiling point and lower vapor pressure and that do not react withePTFE, such as mercury or sodium potassium. In contrast, the network ofinflatable channels 84 can also be expanded during the fixation processor sintering process by use of vapor pressure from a fluid disposedwithin the network of inflatable channels 84. For example, the networkof inflatable channels 84 can be filled with water or a similar fluidprior to positioning assembly in the oven, as discussed above. As thetemperature of the graft body section 15 and network of inflatablechannels 84 begins to heat, the water within the network of inflatablechannels 84 begins to heat and eventually boil. The vapor pressure fromthe boiling water within the network of inflatable channels 84 willexpand the network of inflatable channels 84 provided the vapor isblocked at the inflation line 85 or otherwise prevented from escapingthe network of inflatable channels.

FIG. 18 shows an elevational view in partial longitudinal section of anendovascular graft assembly 105 manufactured by the methods and with theapparatus described above. Endovascular graft assembly 105 comprises agraft body section 108 with a proximal end 106, a distal end 107, andcircumferentially oriented inflatable channels 111 shown in an expandedstate. A longitudinal inflatable channel 116 fluidly communicates withthe circumferential inflatable channels 111.

An expandable member in the form of a proximal connector member 112 isshown embedded between proximal end wrap layers 113 of fusible material.An expandable member in the form of a distal connector member 114 islikewise shown embedded between distal end wrap layers 115 of fusiblematerial. The proximal connector member 112 and distal connector member114 of this embodiment are configured to be secured or connected toother expandable members which may include stents or the like, which arenot shown. In the embodiment of FIG. 18, such a connection may beaccomplished via connector elements 117 of the proximal and distalconnector members 112 and 114, which extend longitudinally outside ofthe proximal and distal end wrap layers 113 and 115 away from the graftbody section 108.

The FIG. 18 embodiment of the present invention features junction 118between the distal end wrap layers 115 of fusible material and thelayers of fusible material of a distal end 121 of the graft assemblymain body portion 122. There is likewise a junction 123 between theproximal end wrap layers 113 and the layers of fusible material of aproximal end 124 of the graft assembly main body portion 122. Thejunctions 118 and 123 may be tapered, with overlapping portions that arebound by sintering or thermomechanical compaction of the end wrap layers113 and 115 and layers of the main body portion 122. This junction 123is shown in more detail in FIG. 19.

In FIG. 19, six proximal end wrap fusible material layers 113 aredisposed between three fusible material inner layers 125 and threefusible material outer layers 126 of the main body portion proximal end124.

FIG. 20 illustrates a sectional view of a portion of the distalconnector member 114 disposed within the distal end wrap layers 115 offusible material. Connector member 114 is disposed between three outerlayers 127 of fusible material and three inner layers 128 of fusiblematerial. Optional seams 127A, formed by the methods discussed above,are disposed on either side of distal connector member 114 andmechanically capture the connector member 114. FIG. 21 likewise is atransverse cross sectional view of the proximal connector member 112embedded in the proximal end wrap layers 113 of fusible material.

FIG. 22 illustrates a transverse cross section of the longitudinalinflatable channel 116 formed between main body portion 122 outer layers131 and the main body portion 122 inner layers 132. FIG. 23 is atransverse cross section of graft main body portion 122 showing acircumferential inflatable channel 111 in fluid communication withlongitudinal inflatable channel 116. The circumferential inflatablechannel 111 is formed between the outer layers 131 of fusible materialof main body portion 122 and inner layers 132 of fusible material ofmain body portion 122.

FIG. 24 shows an endovascular graft assembly 205 having a graft bodysection 208 with a proximal end 206, a distal end 207, andcircumferential inflatable channels 211 shown in an expanded state. Aproximal connector member 212 is embedded between proximal end wraplayers 213 of flexible material. A distal connector member 214 isembedded between distal end wrap layers 215 of flexible material. Theproximal connector member 212 and distal connector member 214 areconfigured to be connected to other expandable members or stents (notshown). A longitudinal inflatable channel 216 is disposed in fluidcommunication with the circumferential inflatable channels 211 andextends longitudinally along the graft body section 208. Connectorelements 217 of the proximal and distal connector members 212 and 214extend longitudinally outside of the proximal and distal end wrap layers213 and 215 away from the graft body section 208.

There is a junction 218 between the distal end wrap layers of flexiblematerial 215 and the layers of flexible material of a distal end 221 ofa main body portion 222 of the graft assembly 205. There is also ajunction 223 between the proximal end wrap layers 213 and the layers offlexible material of a proximal end 224 of the main body portion 222 ofthe graft assembly 205. The junctions 218 and 223 may be taperedjunctions with overlapping portions as shown. Junctions 218 may besecured by sintering or thermomechanical compaction of the junction ifthe flexible material consists of a fusible material or the like.

FIG. 25A illustrates a transverse cross section of a portion of thedistal connector member 214 disposed within the distal end wrap layersof flexible material 215 and secured to the end wrap layers by a joint230. Joint 230 includes distal connector member 214, or portion thereof,disposed within a loop portion 231 of a second layer of flexiblematerial 232. The loop portion 231 of the second layer of flexiblematerial 232 is formed by a flap 233 which has been folded back aboutthe distal connector member 214 in a looped configuration and secured toa portion of the second layer of flexible material at a secured portion234.

A first layer of flexible material 235 is disposed inside and upon aninner surface 236 of the second layer of flexible material 232 andcontinues distally to the distal end 207 of the graft body section 208.A third layer of flexible material 237 is disposed upon an outsidesurface 238 of the second layer of flexible material 232 and extendsdistally to the distal end 207 of the graft body section 208. The firstlayer of flexible material 235 and third layer of flexible material 237contact each other and are bonded or secured to each other distal ofjoint 230.

Flap 233 may be secured to the second layer of flexible material 232 bya variety of suitable methods including adhesive bonding,thermomechanical compaction (including, e.g., seam formation, sintering,welding) or the like. The secured portion 234 may also be secured orbonded to the adjacent first layer of flexible material 235 and thirdlayer of flexible material 237 by the same or similar methods. The joint230 is particularly strong and resistant to forces tending to pull thedistal connector member 214 in a distal direction against the end wraplayers 215 being pulled in a proximal direction. The tensile forces ofsuch stress will be distributed into a shear load on the secured portionof the flap 233 which is bonded over a surface area which is largerelative to the surface area of the corresponding portion of the distalconnector member 214.

FIG. 25B illustrates the joint 230 from outside the graft assembly 205with the third layer of flexible material 237 not shown to more clearlyillustrate the construction of joint 230. FIG. 25B shows flap 233secured to the second layer of flexible material 232 at the securedportion 234 which extends across the majority of flap 233 as indicatedby brackets and hatch lines in FIG. 25B. The loop portion 231 isdisposed about the corresponding portion of the distal connector member214. A void 241 is shown where flap 233 has been cut from the secondlayer of flexible material 232 against the first layer of flexiblematerial 235.

FIG. 26 shows an alternative embodiment of a joint 245, similar in somerespects to the joint 230 of FIG. 24, between a transversely orientedmember such as a connector member 246 and end wrap layers of flexiblematerial 247. The connector member 246 is disposed within a loop portion248 of a third layer of flexible material 249 which is formed by a flap251 that is folded back upon the third layer of flexible material 249about the connector member 246. Flap 251 is secured to the third layerof flexible material 249 over a secured portion 252. An additional flap253 formed from a second layer of flexible material 254 is folded backabout the connector member 246, loop portion 248, flap 251 and securedportion 252. Additional flap 253 is secured to flap 251 and third layerof flexible material 254 at an additional secured portion 255.

Proximal of additional flap 253, a fourth layer of flexible material 258is disposed outside and upon an outside surface 261 of the second layerof flexible material 254 and continues distally to the distal end 207 ofthe graft body section 208. Proximal of joint 245, a first layer offlexible material 256 is disposed upon an inside surface 257 of thesecond layer of flexible material 254 and extends distally to the distalend 207 of the graft body section 208. Distal of joint 245, first layerof flexible material 256 and fourth layer of flexible material 258contact each other and are bonded or secured to each other.

Such a nested joint configuration creates a double layered loop portion262 which can increase the tensile strength of joint 245 by providing athicker loop portion 262 which is more resilient to dynamic repetitiveloads imposed on the joint. Such a configuration could be extended toinclude any number of nested loop portions, including 3, 4, 5 or morelayers of flexible material formed into a loop portion 248 about atransversely oriented member such as connector member 246.

In the embodiment depicted in FIGS. 25A and 25B, the flap 233 formedfrom the second layer of flexible material 249 is secured primarily tothe same second layer of flexible material 249. However, FIG. 27illustrates an alternative embodiment of a joint 265 between a connectormember 266 and end wrap layers of flexible material 267. Joint 265 has aflap 268 formed from a third layer of flexible material 271 which isfolded back on itself about the connector member 266. Flap 268 issecured to a second layer of flexible material 272 which is disposedbetween the flap 268 and the third layer of flexible material 271. Flap268 is secured to the second layer of flexible material 272 over asecured portion 273. Proximal of flap 268, a first layer of flexiblematerial 274 is disposed upon an inner surface 275 of the second layerof flexible material 272 and continues distally to the distal end 207 ofthe graft body section 208. Proximal of joint 265, a fourth layer offlexible material 276 is disposed upon an outside surface 277 of thethird layer of flexible material 271 and extends distally to the distalend 207 of the graft body section 208. Distal of joint 265, the firstlayer of flexible material 274 and fourth layer of flexible material 276contact each other and are bonded or secured to each other distal of thejoint 265.

Referring to FIG. 28, an endovascular graft body section 280 having agenerally tubular configuration and a proximal end section 281 whichincludes proximal end wrap layers of flexible material 282 is shown. Acircumferentially oriented member configured as a connector member 283is disposed about the proximal end wrap layers of flexible material 282and includes a ring member 284 configured in a serpentine pattern andconnector elements 285 extending proximally from the ring member 284past a proximal end 286 of the graft body section 280.

A second layer of flexible material 287 having a tubular configurationis disposed upon an outside surface 288 of a first layer of flexiblematerial 289 which also has a generally tubular shape. A third layer offlexible material 291 is disposed upon an outside surface 292 of thesecond layer of flexible material 287. The third layer of flexiblematerial 291 has longitudinal slits 293 formed in a proximal section 294thereof that extend from the proximal end 286 of the graft body section280 to ring member 284. A first flap 295 formed from the third layer offlexible material 291 is shown positioned against the outer surface 292of the second layer of flexible material 287. In order to form a loopportion, the first flap 295 will be folded back on itself in thedirection indicated by the arrow 296. A second flap 297 is shown foldedback on itself in a loop configuration about the ring member 284 of theconnector member 283 to form a loop portion 298.

In FIG. 29, a plurality of flaps 298 are shown folded back to form loopportions 299 about the ring member 284 of the connector member 283 andsuch flaps 298 have been folded over the substantial circumference ofthe ring member 284. Flaps 298 are then secured to the third layer offlexible material 291 over secured portions 300 by any of the methodsdiscussed above. Once flaps 298 are secured, a fourth layer of flexiblematerial 301 is disposed upon an outer surface 302 of the third layer offlexible material 291, the flaps 298, the loop portions 299 and theconnector member 283 as shown in FIG. 30. For some embodiments of anendovascular graft body section 280, the number of flaps 298 that aredisposed about a connector member 283 can be from about 2 to about 24flaps. For certain embodiments, the flaps 298 may vary in size fromabout 1 to about 25 square millimeters.

The fourth layer of flexible material 301 extends to the proximal end286 of graft body section 280 and may be secured in place by adhesivebonding, sintering, welding, thermomechanical compaction or any othersuitable means. In some embodiments, the fourth layer of flexiblematerial 301 may be disposed only over the joint 303 of the graft bodysection 280. Such a joint 303 secures the connector member 283 to theproximal end wrap layers 282 of graft body section 280 with a joint 303that is highly resistant to tensile forces between those components.When the fourth layer of flexible material 301 is secured in place, aninside surface 304 of the fourth layer of flexible material 301 may besecured to an outside surface 305 of the flaps 298 in order to furtherlock the flaps 298 in the loop configuration and further strengthen thejoint 303 between the connector member 283 and the end wrap layers 282of graft body section 280.

FIG. 31 shows a graft section 310 having a generally tubularconfiguration. A second layer of flexible material 311 is disposed uponan outside surface 312 of a first layer of flexible material 313, withboth layers having a generally tubular configuration. A firsttransversely oriented member 314 in the form of a metallic rod isdisposed within a loop portion 315 of a flap 316. The flap 316 is formedfrom a portion of the second layer of flexible material 311 folded backabout the first transversely oriented member 314 and is secured to thesecond layer of flexible material 311 over a secured portion 318 to forma joint 320.

Joint 320 is particularly resistant to tensile forces imposed upon thefirst transversely oriented member 314 in the direction of the arrows321. A second transversely oriented member 322 in the form of a metallicrod is disposed within a loop portion 323 of a flap 324. Flap 324 isformed from a portion of the second layer of flexible material 311folded back about the second transversely oriented member 322 and issecured to the second layer of flexible material 311 over a securedportion 326 to form a joint 327. Joint 327 is particularly resistant totensile forces imposed upon the first transversely oriented member inthe direction of the arrows 328.

FIG. 31 illustrates that the load of any particular tensile force may bedissipated by a joint having certain features of the invention dependingon the configuration and orientation of the flap and secured portion ofthe flap. In the embodiment shown in FIG. 31, opposing tensile forcescould be imposed on the first transversely oriented member 314 and thesecond transversely oriented member 322 and adequately distributed overthe respective secured portions 318 and 326 to the extent that theflexible material of the loop portions 315 and 323 of the respectivejoints 320 and 327 would likely fail prior to the bond at the respectivesecured portions 318 and 326, depending on the relative tensile strengthinherent in the flexible material of the second layer of flexiblematerial 311. This will generally hold true for joints 320 and 327 madewith ePTFE, both uniaxial and multiaxial, as the flexible material layerwherein the secured portion is secured by thermomechanical compaction.

While particular forms of embodiments of the invention have beenillustrated and described, it will be apparent that variousmodifications can be made without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

1-37. (Canceled)
 38. A method for securing a transversely orientedmember to a flexible material portion of an endovascular graft orsection thereof comprising: a) disposing the transversely orientedmember in proximity to a flap in a flexible material portion of anendovascular graft or section thereof; b) folding the flap over at leasta portion of the transversely oriented member to form a looped portionof the flap about the transversely oriented member; and c) securing theflap in the looped configuration.
 39. The method of claim 38 wherein theflap is comprised of a portion of a layer of flexible material and theflap is secured to the layer of flexible material.
 40. The method ofclaim 38 wherein the flap is secured in the looped configuration withadhesive.
 41. The method of claim 38 wherein the flap is comprised of aportion of a first layer of flexible material and the flap secured to aportion of a second layer of flexible material.
 42. The method of claim38 wherein the flexible material comprises ePTFE.
 43. The method ofclaim 42 wherein the flap is secured in the looped configuration bythermomechanical compaction.
 44. The method of claim 42 wherein the flapis secured in the looped configuration with FEP or PFA.
 45. The methodof claim 42 wherein the ePTFE material of the flap is sintered afterbeing secured in the looped configuration.
 46. A method for securing acircumferentially oriented member to a flexible material portion of anendovascular graft or section thereof comprising: a) disposing acircumferentially oriented member in proximity to a flap in a flexiblematerial portion of an endovascular graft or section thereof; b) foldingthe flap over at least a portion of the circumferentially orientedmember to form a looped portion of the flap about the circumferentiallyoriented member; and c) securing the flap in the looped configuration.47. The method of claim 46 wherein the flap is comprised of a portion ofa layer of flexible material and the flap is secured to the layer offlexible material.
 48. The method of claim 46 wherein the flap issecured in the looped configuration with adhesive.
 49. The method ofclaim 46 wherein the flap is comprised of a portion of a first layer offlexible material and the flap secured to a portion of a second layer offlexible material.
 50. The method of claim 46 wherein the flexiblematerial comprises ePTFE.
 51. The method of claim 50 wherein the flap issecured in the looped configuration by thermomechanical compaction. 52.The method of claim 50 wherein the flap is secured in the loopedconfiguration with FEP or PFA.
 53. The method of claim 50 wherein theePTFE material of the flap is sintered after being secured in the loopedconfiguration.
 54. A method for securing an expandable member to aflexible material portion of an endovascular graft or section thereofcomprising: a) disposing the expandable member in proximity to a flap ina flexible material portion of an endovascular graft or section thereof;b) folding the flap over at least a portion of the expandable member toform a looped portion of the flap about the expandable member; and c)securing the flap in the looped configuration.
 55. The method of claim54 wherein the flap comprises a portion of a layer of flexible materialand the flap is secured to the layer of flexible material.
 56. Themethod of claim 54 wherein the flap is secured in the loopedconfiguration with adhesive.
 57. The method of claim 54 wherein the flapcomprises a portion of a first layer of flexible material and the flapsecured to a portion of a second layer of flexible material.
 58. Themethod of claim 54 wherein the flexible material comprises ePTFE. 59.The method of claim 58 wherein the flap is secured in the loopedconfiguration by thermomechanical compaction.
 60. The method of claim 58wherein the flap is secured in the looped configuration with FEP or PFA.61. The method of claim 58 wherein the ePTFE material of the flap issintered after being secured in the looped configuration.